The carboxylic acid esters of .gamma.-hydroxy-tiglic aldehyde are known intermediates for vitamin A and various perfumistic products. These esters have been prepared from 1,1-dimethoxy-2-methyl-but-3-en-2-ol. See U.S. Pat. No. 3,760,004, Sept. 18, 1973, Freyschlag et al. and U.S. Pat. No. 3,347,930, Oct. 17, 1967, Freyschlag et al. Another starting material such as the bismonocarboxylic acid ester of but-1-ene-3,4-diol also has been used as a starting material for these esters of .gamma. hydroxy-tiglic-aldehyde. See U.S. Pat. No. 3,732,287--Himmele et al., May 8, 1973.
Recently in U.S. Pat. No. 3,661,980, Himmele et al., May 9, 1972, it has been proposed to prepare these esters of .gamma.-hydroxy-tiglic aldehyde from esters of but-2-ene-1,4-diol. However, this synthesis as well as the synthesis from the esters of but-1-ene-3,4-diol has not proven to be economical since pressures of from 300 to 1,000 atmospheres are utilized to obtain the desired product. The use of these very high pressures involves the use of expensive equipment and costly handling procedures which mitigates against the commercialization of this process. Therefore, a simple and economic process for converting these relatively inexpensive but-2-ene diols to esters of .gamma. -hydroxy tiglic aldehyde is desired.